U.S. DOMESTIC AIRLINE FUEL EFFICIENCY RANKING, 2017-2018
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WHITE PAPER SEPTEMBER 2019
U.S. DOMESTIC AIRLINE FUEL
EFFICIENCY RANKING, 2017-2018
Xinyi Sola Zheng; Brandon Graver, Ph.D.; Dan Rutherford, Ph.D.
www.theicct.org
communications@theicct.org
BEI J I NG | BERLIN | B R U SS E LS | SAN FRANCIS CO | WAS H INGTO NACKNOWLEDGMENTS The authors thank Amy Smorodin for her review and Kevin Zhang for refining the Python code to streamline the statistical analysis. We also acknowledge Airline Data Inc. for providing processed BTS data T-100 and Form 41 data. International Council on Clean Transportation 1500 K Street NW Suite 650 Washington DC 20005 USA communications@theicct.org | www.theicct.org | @TheICCT © 2019 International Council on Clean Transportation
U.S. DOMESTIC AIRLINE FUEL EFFICIENCY RANKING, 2017-2018
TABLE OF CONTENTS
INTRODUCTION...........................................................................................................................1
METHODOLOGY......................................................................................................................... 2
FINDINGS.....................................................................................................................................4
High level findings.....................................................................................................................................4
Key airline findings.................................................................................................................................... 5
Operational variables influencing airline fuel efficiency............................................................. 7
Industrywide changes in demand, fuel efficiency, and fuel use..............................................9
CONCLUSIONS.......................................................................................................................... 10
REFERENCES............................................................................................................................. 11
APPENDIX: 2017 RESULTS......................................................................................................13
LIST OF FIGURES
Figure 1. Fuel Efficiency Scores and excess fuel per unit transport service
by airline for U.S. domestic operations, 2018..................................................................................4
Figure 2. Share of regional departures by aircraft type for Alaska and
all carriers, 2016 and 2018.......................................................................................................................6
Figure 3. United States domestic passenger airline fuel use and RPMs
per gallon of fuel, 2005-2018.................................................................................................................9
LIST OF TABLES
Table 1. Airline fuel efficiency rankings for U.S. domestic operations, 2014 to 2018............ 5
Table 2. Explanatory variables for fuel efficiency, 2018................................................................... 8
Table A1. Fuel Efficiency Scores and excess fuel per unit transport service
by airline for U.S. domestic operations, 2017................................................................................. 13
Table A2. Explanatory variables for fuel efficiency, 2017...............................................................14
iICCT WHITE PAPER
INTRODUCTION
Aviation is an important part of the global economy, and demand for aviation services is
growing. Passenger miles traveled on U.S. airlines are expected to increase 2.2% annually
through 2039 (FAA, 2019a). In 2018, commercial aircraft emitted about 900 million
tonnes of CO2 globally (IATA, 2019), which is 2.4% of the worldwide total and more than
the entire German economy. Commercial aviation in the United States, which accounts
for 30% of global aviation emissions (U.S. EPA, 2016), has been meeting its self-imposed
goal to improve fleetwide fuel efficiency by 1.5% annually (Graver, 2018). However, total
fuel burn increased by 16% from 2009 to 2017 due to growing demand (Graver and
Rutherford, 2018).
Recognizing the importance of reducing aviation emissions, the U.S. government set
a goal of capping CO2 emissions from U.S. commercial carriers at 2005 levels from
2020 (FAA, 2015). In support of this goal, the Federal Aviation Administration (FAA)
implemented a voluntary system to collect CO2 emissions data from airlines (FAA,
2019b). This data will be used to support the International Civil Aviation Organization
(ICAO) Carbon Offsetting and Reduction Scheme for International Aviation, or CORSIA,
starting in 2021 (Olmer & Rutherford, 2017a). The U.S. Environmental Protection Agency,
which is obligated to set an aircraft greenhouse gas emissions standard under the
Clean Air Act, is expected to propose a rule that, at a minimum, conforms with ICAO’s
recommended standard (U.S. EPA, 2016) in fall of 2019 (Office of Management and
Budget, 2019).
Individuals, companies, and organizations are increasingly interested in taking action
to reduce the carbon footprint of their air travel. Ideally, airlines would provide fuel
efficiency data directly to consumers to help them choose more fuel-efficient flights.
However, assessments of which carriers are more and less fuel-efficient can also provide
value. In 2013, the ICCT began to publish annual fuel efficiency rankings of major U.S.
domestic airlines, beginning with data from 2010.1 This update ranks the fuel efficiency
of U.S. airlines in 2017 and 2018.
1 The previous rankings include: Zeinali, et al. 2013; Kwan, Rutherford & Zeinali, 2014; Kwan & Rutherford, 2014;
Li, Kwan & Rutherford, 2015; and Olmer & Rutherford, 2017b
1U.S. DOMESTIC AIRLINE FUEL EFFICIENCY RANKING, 2017-2018
METHODOLOGY
This update, as in the previous studies, evaluates the fuel efficiency of U.S. airlines’
domestic operations using a deterministic frontier model. The frontier approach
benchmarks carriers using a fuel per transport service metric based on data reported by
airlines to the U.S. Department of Transportation’s Bureau of Transportation Statistics
(BTS) (Airline Data, Inc. 2019).2
Transport service accounts for both mobility, measured by revenue passenger miles
(RPMs), and access, measured by the number of airports served or flight frequency. This
ensures the model equitably compares airlines operating under various business models
(e.g. point-to-point vs. hub-and-spoke, predominately short haul vs. longer coast-to-
coast flights, etc.). The fuel consumed per unit of transport service is compared to that
of the average airline, by quarter, in order to generate a Fuel Efficiency Score (FES),
which is discussed below.
Quarterly data on RPMs, departures, and fuel burn data for 2017 and 2018 either
extracted from BTS database or provided by Airline Data, Inc (2019) are used to develop
the statistical frontier model, which relates the fuel consumed by an airline i at time t to
its revenue passenger miles (RPM) and departures (dep):
fuelit = f(RPMit , depit) + ηit [Eq. 1]
where ηit represents the airline’s true inefficiency.
Assuming a log-linear function best describes the relationship between the input and
output variables, Equation 1 is transformed into the following functional form:
ln (fuel)it = β0 + β1ln (RPM)it + β2ln (dep)it + ξit [Eq. 2]
where b0, b1, and b2 are the coefficients estimated from a single year’s quarterly dataset
of fuel consumption, RPMs, and departures. Some air carriers operate a significant
portion of their flights through the use of regional affiliates. To account for this, the
RPMs, departures, and fuel use of regional affiliates are apportioned to their respective
mainline carriers using BTS T100 data (U.S. DOT, 2019). The function also takes into
account circuity, measured as the degree to which air carriers’ flight paths deviate from
direct origin-destination distance as a result of layovers (Zeinali, Rutherford, Kwan, &
Kharina, 2013).
In some cases, air carriers misreport their fuel burn, RPMs, or departures to BTS. When
possible, we corrected the data using revised data supplied by the air carrier itself.
When not possible, erroneous data was backfilled using the relationship between fuel
burn and RPMs for that aircraft type. For example, if an airline’s Quarter 1 2018 fuel burn
value for a specific aircraft type was determined to be an outlier, the fuel burn was
backfilled based on a linear regression for that specific air carrier and aircraft type from
other quarters in 2017 and 2018.
2 For an in-depth discussion on the Frontier model methodology, see Zou et al. (2012).
2ICCT WHITE PAPER
The resulting frontier model representing 2017 airline fuel consumption, with standard
error in parentheses, is:
ln (fuel) = 0.599 + 0.611 × ln (RPM) + 0.373 × ln (dep) [Eq. 3]
(1.006) (0.073) (0.060)
Number of observations: 48 R2: 0.997
Similarly, the resulting frontier model representing 2018 airline fuel consumption, with
standard error in parentheses, is:
ln (fuel) = 0.857 + 0.580 × ln (RPM) + 0.411 × ln (dep) [Eq. 4]
(1.194) (0.087) (0.071)
Number of observations3: 48 R2: 0.997
To compare the efficiency of airlines irrespective of business model, a unitless Fuel
Efficiency Score (FES) was developed. The FES measures the transport service
(including both mobility and access) per unit of fuel consumed and is calculated by
normalizing each airline’s inefficiency value by the simple average across all airlines.
Thus, a higher FES (>1) indicates relatively higher fuel efficiency, while a lower FES (U.S. DOMESTIC AIRLINE FUEL EFFICIENCY RANKING, 2017-2018
FINDINGS
This paper identifies four key findings from the research: the rankings of the relative fuel
efficiency of airlines in 2018; trends in the fuel efficiency of airlines over time; operational
variables that explain these trends; and industrywide changes in demand, fuel efficiency,
and fuel use.
HIGH LEVEL FINDINGS
The 2018 Fuel Efficiency Scores for U.S. domestic air carriers are presented in Figure
1. Carriers with an efficiency score greater than 1.00 are more fuel efficient than the
industry average, while carriers with a score less than 1.00 are less efficient than
average. Excess fuel burn per unit transport service4, calculated by passenger miles and
departures weighted by the coefficients in Equation 4, relative to the most fuel-efficient
carrier are shown at the right of the diagram. The analysis of fuel efficiency from 2017
operations are summarized in the Appendix.
Excess Fuel
Per Unit
Transport Service
1. Frontier 1.11 —
2. Spirit 1.04 +7%
2. Southwest 1.04 +7%
4. Sun Country 1.02 +9%
5. Alaska 1.01 +10%
5. United 1.01 +10%
5. Allegiant 1.01 +10%
8. Delta 0.96 +15%
8. American 0.96 +15%
10. Hawaiian 0.95 +17%
11. JetBlue 0.88 +26%
0.8 0.90 1.0 1.1
Fuel Efficiency Score (longer bars = more efficient);
FES = 1.00 represents industry average
Figure 1. Fuel Efficiency Scores and excess fuel per unit transport service by airline for U.S.
domestic operations, 2018.
As shown in Figure 1, Frontier operated the most fuel-efficient domestic operations
in 2018 by a significant margin. Spirit and Southwest tied for second in terms of fuel
4 Transport service denotes the combination of RPMs and departures provided by each airline, weighted
by their relative importance as a driver of fuel consumption under a deterministic frontier regression.
See the methodology section above. For 2018, each airline’s transport service can be calculated as
(RPM)^0.580*(dep)^0.411.
4ICCT WHITE PAPER
efficiency on domestic flights, burning 7% more fuel to provide the same amount of
transport service as Frontier. Sun Country, which began restructuring to an ultra-low-
cost carrier in 2017 (Moseley, 2017), placed fourth in terms of fuel efficiency. Alaska,
United, and Allegiant rounded out the carriers with above average fuel efficiency in 2018.
United has consistently operated the most fuel-efficient domestic operations of the
largest hub-and-spoke legacy carriers since merging with Continental Airlines in 2012.
Four carriers—Delta, American, Hawaiian, and JetBlue—all had fuel efficiencies worse
than the industry average. Delta and American operated the eighth most fuel-efficient
domestic flights in 2018 with efficiency scores of 0.96. Hawaiian, whose fuel efficiency
has dropped five spots since 2016, ranked 10th in 2018. JetBlue operated the least
fuel-efficient U.S. domestic operations by a wide margin in 2018. The gap between
best-performing Frontier and worst-performing JetBlue was 26% in 2018, equal to that
observed in 2016 (Olmer & Rutherford, 2017), although slightly narrower than the 27%
gap seen in 2017 (see Appendix).
KEY AIRLINE FINDINGS
The airline fuel efficiency rankings from 2014 to 2018 are presented in Table 1.5 The table
highlights the shift in ranking over time as well as mergers (arrows) and fuel-efficiency
rank ties (asterisks). As a result of the American-U.S. Airways and Alaska-Virgin America
mergers, the total number of airlines in this series dropped from 13 in 2014 to 11 in 2018.
Table 1. Airline fuel efficiency rankings for U.S. domestic operations, 2014 to 2018.
Rank 2014 2015 2016 2017 2018 Rank
1 Alaska Alaska Alaska Frontier Frontier 1
2 Spirit Spirit Frontier Alaska* Spirit* 2
3 Frontier Frontier Spirit Spirit* Southwest* 3
4 Southwest Southwest Southwest Southwest Sun Country 4
5 United Hawaiian* Hawaiian Sun Country Alaska* 5
6 Hawaiian United* Sun Country* United* United* 6
7 U.S. Airways Sun Country United* Hawaiian* Allegiant* 7
8 Allegiant Delta American American Delta* 8
9 JetBlue Allegiant* Allegiant* Allegiant* American* 9
10 Sun Country American* Delta* Delta* Hawaiian 10
11 Delta JetBlue* JetBlue JetBlue JetBlue 11
12 Virgin America Virgin America Virgin America Virgin America —
13 American — — — —
* Denotes ties between airlines in a given year
Beginning in 2017 (see Appendix), Frontier took over the top spot in the ranking
from Alaska, which held the distinction of being the most fuel-efficient U.S. domestic
airline from 2010 to 2016. In October 2016, Frontier began receiving new Airbus
A320neo aircraft with more efficient Leap-1A engines and wingtip devices (Airbus,
2016). As of July 2019, Frontier has 43 A320neo aircraft in service (Z. Kramer, personal
communication, August 2019), more than any other U.S. carrier. It ordered an additional
134 aircraft from the A320neo family in December 2017 through its parent company
(eTurboNews, 2017), pointing to further improvements in future rankings.
5 See Olmer and Rutherford (2017) for the equivalent rankings for 2010 to 2013.
5U.S. DOMESTIC AIRLINE FUEL EFFICIENCY RANKING, 2017-2018
Spirit Airlines, an ultra-low-cost carrier with operating bases in Detroit, Fort Lauderdale,
Las Vegas, and five other cities, has consistently ranked second or third in fuel efficiency
since 2010. Southwest Airlines, which flies an all-Boeing 737 fleet throughout the U.S.,
moved from fourth place for fuel efficiency in 2016 to a tie with Spirit for second place
in 2018. Southwest’s improving fuel efficiency has been tied to fleet modernization, as
the company is retiring its older and smaller 737-300 aircraft in favor of larger and more
fuel-efficient 737 Next Generation and 737 MAX aircraft (Ewing, 2017).
Alaska slipped four ranks in fuel efficiency from 2016 to 2018 due in large part to its merger
with Virgin America, which operated the least fuel-efficient U.S. domestic flights from 2015
to 2017. The merger resulted in a percentage point drop in load factor from 85% to 84%
and a 2% reduction in seating density from 2016 to 2018. The fuel efficiency of Alaska’s
regional operations also fell due to the greater use of regional jets instead of more efficient
turboprop aircraft. In 2016, Alaska’s affiliate Horizon Air flew 132,000 turboprop flights, or
one half of all such flights in the United States. By 2018, Alaska’s regional turboprop flights
fell by about one-quarter, from 82% of regional flights in 2016 to 55% in 2018 (Figure 2).6
Over the same period, Alaska’s use of less fuel-efficient regional jets increased from 18% to
45% of regional operations. The share of regional flights completed by turboprops for all
airlines, including Alaska, fell from 8% in 2016 to 4% in 2018.
Alaska regional departures by aircraft type
2016 2018
18%
45%
55%
82%
All carrier regional departures by aircraft type
2016 2018 4%
8%
92% 96%
Turboprop Regional jet
Figure 2. Share of regional departures by aircraft type for Alaska and all carriers, 2016 and 2018.
6 Here, we define regional operations as those flown by turboprop and regional jets only.
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This shift in aircraft type reduced the fuel efficiency of Alaska’s regional operations and,
therefore, the carrier’s overall fuel efficiency. Fuel burn per revenue passenger mile for
Alaska’s affiliates increased by 11%, and fuel burn per departure increased by 35% from
2016 to 2018. Combined with its merger with Virgin America, these changes contributed
to Alaska dropping from the most fuel-efficient carrier in 2016 to a tie for fifth in 2018.
A few other shifts are apparent in the ranking. Hawaiian slipped five efficiency ranks
from 2016 to 2018 on account of fewer turboprop operations, increased premium
economy seating on its A330 aircraft, and an 5% decrease in the average size of aircraft7
used for domestic operations. Together, these changes led to an 8% decrease in the
average number of seats per Hawaiian flight, from 273 in 2016 to 253 in 2018. The least
fuel-efficient carrier in 2018, JetBlue, has held steady in 11th place since 2015. JetBlue
operates its fleet of Airbus A320, Airbus A321, and Embraer 190 aircraft at a lower load
factor and with fewer seats per plane compared to its competitors. JetBlue’s order of 60
A220 aircraft, along with options for 60 more in July 2018 (Leeham News, 2018) could
improve its fuel efficiency on future rankings.
OPERATIONAL VARIABLES INFLUENCING AIRLINE FUEL
EFFICIENCY
Table 2 summarizes key airline operational parameters for the 11 carriers included in this
survey, including absolute and share of RPMs, passenger load factor, seating density in
seats per m2 of floor area8, and the relative fuel burn9 of each airline’s combined mainline
and regional fleets. The table also identifies circuity, a ratio of actual distance traveled
by passengers to the great circle distance between origin and destination airports. A
circuity of 1.00 corresponds to direct flights only, while a value of 1.06 represent 6%
excess miles traveled due to less efficient routing.
7 RPM-weighted average of square meters of pressurized floor area using the metric of Reference Geometric
Factor, or RGF. RGF was developed by the International Civil Aviation Organization as a means to help assess
aircraft fuel efficiency. See Rutherford (2013) for further details.
8 As measured by seats per square meter of RGF. See footnote 7 for details.
9 As measured by margin from the International Civil Aviation Organization’s fuel efficiency (CO2) standard,
which established a means of assessing and comparing aircraft efficiency independent of how it is used in
actual operations. Lower values indicate more fuel-efficient fleets, while higher values indicate more fuel-
intensive aircraft. See Rutherford & Kharina (2017) for details.
7U.S. DOMESTIC AIRLINE FUEL EFFICIENCY RANKING, 2017-2018
Table 2. Explanatory variables for fuel efficiency, 2018
Domestic RPMs
Passenger Seating densitya Aircraft
Rank Airline Billion % load factor (seats/m2) fuel burnb Circuityc
1 Frontier 20 3% 86% 1.71 +3.0% 1.01
2 Spirit 28 4% 85% 1.68 +3.7% 1.01
2 Southwest 129 18% 83% 1.71 +4.5% 1.03
Sun
4 3 0.4% 81% 1.66 +5.4% 1.00
Country
5 Alaskad 52 7% 84% 1.50 +7.2% 1.03
5 United 132 18% 85% 1.39 +4.7% 1.04
5 Allegiant 12 2% 85% 1.69 +11.2% 1.00
8 Delta 141 20% 86% 1.44 +9.2% 1.06
9 American 152 21% 84% 1.36 +4.0% 1.05
10 Hawaiian 12 2% 87% 1.21 +1.5% 1.01
11 JetBlue 40 6% 85% 1.37 +4.3% 1.01
RPM weighted average 85% 1.45 +5.5% 1.04
[a] As measured by seats per square meter of RGF. See footnote 7 for details.
[b] As measured by the average margin of aircraft to ICAO’s CO2 standard. See footnote 9 for details.
[c] A circuity of 1.00 corresponds to direct flights only, while a value of 1.06 represent 6% excess miles traveled
due to less efficient routing.
[d] Post-merger value including Virgin America flights. 2017 results, summarized in the Appendix, include Virgin
America as an independent carrier.
As summarized in Table 2, key operational parameters of U.S. domestic operations varied
less compared to previous years, reflecting the move by most U.S. carriers toward a low-
cost business model since 2010. For example, carrier load factors varied from 70% (Sun
Country) up to 90% (Allegiant) in 2010, compared to the narrower load-factor range
of 81% (Sun Country) to 87% (Hawaiian) in 2018. Likewise, the fuel burn of Allegiant’s
fleet of predominately older A320 family aircraft was about 10 percentage points higher
than Hawaiian’s fuel burn, which on average operated the most fuel-efficient aircraft in
2018. In 2010, there was 27 percent difference in a comparable metric10, when Allegiant
operated only very inefficient McDonnell Douglas MD-80 aircraft compared to Alaska’s
much more fuel-efficient Boeing 737 Next Generation aircraft (Zeinali et al., 2013).
The data in Table 2 provides evidence for Frontier’s superior fuel-efficiency performance
in 2018. In addition to operating the second most fuel-efficient fleet, Frontier operated
with an above average load factor (86%) and low circuity (1.01), and tied with Southwest
for the highest seating density (1.71 seats/m2). In other words, Frontier operated
predominately direct flights on fuel-efficient aircraft with more passengers than most
other airlines. Spirit and Southwest were broadly comparable in these measures to
Frontier. Carriers with lower, but still above average fuel efficiencies —Alaska, United,
and Allegiant—tended to either operate less fuel-efficient fleets with fewer passengers
and/or with higher circuity than their better performing peers. Operations of airlines
with below-average fuel efficiency tended to compare poorly on multiple variables.
10 Technology Utilization Score (TUS), a metric developed to compare the relative fuel burn of each airline’s
fleet in the 2010 study, was used by ICCT prior to ICAO’s CO2 standard metric. See Zeinali et al. (2013) for
further details.
8ICCT WHITE PAPER
INDUSTRYWIDE CHANGES IN DEMAND, FUEL EFFICIENCY,
AND FUEL USE
From 2016 to 2018, increases in the number of U.S. domestic flights continued to
outstrip improvements in fuel efficiency. Overall, RPMs by the ranked carriers increased
by 10% from 2016 to 2018, identical to the increase seen from 2014 to 2016 (Olmer &
Rutherford, 2017). Fuel efficiency, measured in RPMs per gallon of fuel, improved by
3% from 2016 to 2018. The net result was a 7% increase in overall fuel burn and CO2
emissions from U.S. domestic operations. Fuel use from domestic operations by U.S.
passenger carriers hit 12.5 billion gallons in 2018, a 17% increase since the 2009 minimum
during the global financial crisis (Figure 3) and above 2005 levels.11
14 60
Gallons of Fuel RPMs/fuel
55
U.S. airline fuel use (billion gallons)
RPMs per gallon of fuel
2005 Fuel Consumption 50
12 45
40
35
10 30
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
Year
Figure 3. United States domestic passenger airline fuel use and RPMs per gallon of fuel, 2005-2018.
11 Gallons of fuel for 2005 to 2009 shown in Figure 3 are directly from BTS Form-41 data. Fuel use from 2010 is
drawn from previous ICCT studies with corrections of erroneously reported data from carriers as described in
the methodology section above.
9U.S. DOMESTIC AIRLINE FUEL EFFICIENCY RANKING, 2017-2018
CONCLUSIONS
This study assessed the fuel efficiency of U.S. airlines on domestic operations in the
years 2017 and 2018. For the first time, Frontier’s fuel efficiency on domestic flights
exceeded that of Alaska Airlines, which fell to 5th due to its merger with less efficient
Virgin America and its reduced use of highly efficient turboprop aircraft. Spirit and
Southwest tied for second place in the ranking, burning 7% more fuel per unit transport
service than Frontier. Frontier’s widespread use of new, more fuel-efficient Airbus
A320neo aircraft, along with its operational practices, accounted for its superior
efficiency. Conversely, JetBlue took the lowest spot on the ranking, burning 26% more
fuel than Frontier to provide a similar level of transport service.
Domestic airline operations continued to expand, with increases in fuel efficiency
outstripped by an overall increase in activity. Revenue passenger miles increased 10%
and departures increased by 4% from 2016 to 2018. Fuel efficiency in terms of RPMs per
gallon of fuel consumed improved by 3%. The net result was a 7% increase in overall fuel
burn and CO2 emissions from domestic passenger operations. CO2 emissions from U.S.
domestic operations have increased by 15% over the past five years, raising questions
about how the U.S. aviation industry can meet its goal of carbon neutral growth from
2020 without further policy interventions.
Future updates to this series will investigate how changes in industry structure,
overall aviation activity, and new technologies influence airline efficiency. As industry
consolidation solidifies, for example through the full integration of Virgin America’s
operations by Alaska (Gates, 2019), we may expect corresponding changes in the
relative fuel efficiency of the remaining carriers. Likewise, the expanded market share of
more efficient single-aisle aircraft types, like the Airbus A320neo, Boeing 737 MAX, and
the Airbus A220 (formerly the Bombardier CSeries), should improve the fuel efficiency
of more U.S. carriers.
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United States Environmental Protection Agency (U.S. EPA). (2016). EPA Determines
that Aircraft Emissions Contribute to Climate Change Endangering Public Health
and the Environment. News release. Retrieved from https://archive.epa.gov/epa/
newsreleases/epa-determines-aircraft-emissions-contribute-climate-change-
endangering-public-health.html
Zeinali, M., Rutherford, D., Kwan, I., & Kharina, A. (2013). U.S. domestic airline fuel
efficiency ranking, 2010. Retrieved from the International Council on Clean
Transportation http://www.theicct.org/publications/us-domestic-airline-fuel-efficiency-
ranking-2010
Zou, B., Elke, M., & Hansen, M. (2012). Evaluating air carrier fuel efficiency and CO2
emissions in the U.S. Airline Industry. Retrieved from the International Council on Clean
Transportation http://www.theicct.org/evaluating-air-carrier-fuel-efficiency-and-co2-
emissions-us-airline-industry
12ICCT WHITE PAPER
APPENDIX: 2017 RESULTS
The table below (Table A1) shows the Fuel Efficiency Scores and excess fuel use for U.S.
domestic carriers in 2017. Carriers with an efficiency score greater than 1.00 are more
fuel efficient than the industry average, while carriers with a score less than 1.00 are less
efficient than average.
Table A1. Fuel Efficiency Scores and excess fuel per unit transport service by airline for U.S.
domestic operations, 2017.
Excess Fuel Per Unit
Rank Airline FES Transport Service
1 Frontier 1.11 —
Alaska 1.07 +4%
2
Spirit 1.07 +4%
4 Southwest 1.04 +7%
5 Sun Country 1.03 +8%
United 1.00 +11%
6
Hawaiian 1.00 +11%
8 American 0.98 +13%
Allegiant 0.96 +15%
9
Delta 0.96 +15%
11 JetBlue 0.91 +21%
12 Virgin America 0.87 +27%
Frontier exceeded Alaska in domestic fuel efficiency in 2017. Spirit tied with Alaska in
domestic fuel efficiency in 2017, burning 4% more fuel than Frontier on comparable
domestic flights. Southwest, ranked 4th, and Sun Country, ranked 5th, rounded out the
group of five carriers with better-than-average fuel efficiency. United and Hawaiian
tied for sixth with FESs equal to the average industry (1.00). In 2017, United continued
to operate the most fuel-efficient domestic operations of the largest hub-and-spoke
legacy carriers, a distinction it has held since merging with Continental Airlines in 2012.
Five carriers—American, Allegiant, Delta, JetBlue, and Virgin America—had fuel
efficiencies below the industry average. American and Delta continued their positions
as more fuel intensive legacy carriers, burning 13 to 15% more fuel than Frontier on
comparable flights. JetBlue (0.91) and Virgin America (0.87) were ranked the most
inefficient carriers. Virgin America burned 27% more fuel per unit transport service than
Frontier in 2017, the largest gap seen in U.S. domestic operations since 2013 (Kwan &
Rutherford, 2014).
13U.S. DOMESTIC AIRLINE FUEL EFFICIENCY RANKING, 2017-2018
Table A2 summarizes the key explanatory variables for airline fuel efficiency in 2017.
Table A2. Explanatory variables for fuel efficiency, 2017
RPMs Seating
Passenger densitya Aircraft
Rank Airline Billion % of total load factor (seats/m2) fuel burnb Circuityc
1 Frontier 18 3% 87% 1.69 6.7% 1.01
Alaska 37 5% 85% 1.53 7.4% 1.03
2
Spirit 23 3% 83% 1.67 3.9% 1.01
4 Southwest 125 18% 84% 1.72 5.2% 1.03
5 Sun Country 3 0.4% 80% 1.58 5.5% 1.01
United 124 18% 85% 1.37 4.8% 1.04
6
Hawaiian 11 2% 88% 1.22 2.4% 1.01
8 American 149 22% 84% 1.37 4.4% 1.05
Allegiant 11 2% 84% 1.68 18.0% 1.00
9
Delta 134 20% 86% 1.43 10.1% 1.06
11 JetBlue 37 5% 85% 1.37 4.3% 1.01
12 Virgin America 13 2% 84% 1.38 7.2% 1.01
RPM weighted average 85% 1.48 6.2% 1.04
[a] As measured by seats per square meter or RGF. See footnote 7 in the main body of the report for details.
[b] As measured by the average margin of aircraft to ICAO’s CO2 standard. See footnote 9 in the main body of the report
for details.
[c] A circuity of 1.00 corresponds to direct flights only, while a value of 1.06 represent 6% excess miles traveled due to
less efficient routing.
A few observations can be made from Table A2. Frontier’s fuel efficiency is linked to
the large numbers of passengers it carried on its flights owing to high load factors and
dense seating configuration, second only to Southwest. It’s fleet, however, was slightly
less fuel-efficient than the average in 2017 relative to ICAO’s international efficiency
benchmark. Alaska was less fuel-efficient than Frontier on each of these metrics, but
almost matched on overall efficiency due to the widespread use of turboprops for
regional flights (see Figure 2 and accompanying text).
Fourth-ranked Southwest had the highest seating density (1.72 seats/m2) in 2017, but
was roughly average in terms of load factor, fleet efficiency, and circuity. Hawaiian’s high
load factor and efficient fleet was largely offset by greater premium seating offerings on
flights to the mainland United States. The two least fuel-efficient carriers, JetBlue and
Virgin America, demonstrated similar load factors, seating configurations, and circuity,
although Virgin America operated a less fuel-efficient fleet. Allegiant, which flew 38% of
its RPMs on MD-80 aircraft in 2017, had the most fuel intensive fleet by a wide margin,
almost 16 percentage points worse than best-performing Hawaiian.
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